Gearbox for vehicles

ABSTRACT

A gearbox for vehicles, comprising a split gearbox ( 15 C), a main gearbox ( 15 A) and a range gearbox ( 15 B), which is shiftable into a low range gear, a high range gear and a reverse gear; the range gearbox ( 15 B) comprising a planetary gear ( 14 ) with a ring gear wheel ( 22 ), a sun gear wheel ( 18 ) and a planet carrier ( 20 ), on which at least one planet gear wheel ( 24 ) is rotatable mounted, which ring gear wheel ( 22 ) and sun gear wheel ( 18 ) engage with the at least one planet gear wheel ( 24 ); a gearbox housing ( 12 ) surrounding the planetary gear ( 14 ); a first axially movable coupling sleeve ( 42 ) arranged to engage the planet carrier ( 20 ) with the gearbox housing ( 12 ); and a second axially movable coupling sleeve ( 43 ) arranged to engage the ring gear wheel ( 22 ) with an output shaft ( 28 ) for achieving the reverse gear in the gearbox ( 2 ). The split gearbox ( 15 C) and the main gearbox ( 15 A) are together arranged to have a combined largest gear ratio which is larger than the gear ratio in the planetary gear ( 14 ) in the range gearbox ( 15 B) when the planetary gear ( 14 ) is shifted into the reverse gear.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §§ 371 national phase conversionof PCT/SE2018/050067, filed Jan. 31, 2018, the contents of which areincorporated herein by reference which claims priority of Swedish PatentApplication No. 1750108-1, filed Feb. 8, 2017, the contents of which areincorporated by reference herein. The PCT International Application waspublished in the English language.

FIELD OF THE INVENTION

The present invention relates to a gearbox for vehicles and to a vehiclecomprising such a gearbox.

BACKGROUND AND PRIOR ART

In vehicles, especially heavier vehicles such as trucks, the gearboxcomprises a main gearbox and often also a range gearbox, which isconnected to the main gearbox. The range gearbox doubles the number ofgears in the gearbox. The range gearbox usually includes a planetarygear, which has a low gear and a high gear, so that the gearbox can bedivided into a low range gear position and a high range gear position.In the low range gear position, a downshift takes place through theplanetary gear, and in the high range gear position, the gear ratio is1:1 in the planetary gear.

The range gearbox is usually provided between the main gearbox and apropeller shaft coupled to the drive wheels of the vehicle. The rangegearbox is accommodated in a gearbox housing. It comprises an inputshaft coupled to the main gearbox, an output shaft, and the planetarygear, which is disposed between the input shaft and the output shaft.The planetary gear usually comprises three components, which arerotatably arranged relative to each other, namely a sun gear wheel, aplanet carrier with planet gear wheels and a ring gear wheel. Withknowledge of the number of teeth of the sun gear wheel and the ring gearwheel, the relative speed of the three components can be determinedduring operation. In a range gearbox, the sun gear wheel can berotatably connected to the input shaft, a number of planet gear wheelswhich engage the sun gear wheel, which planet gear wheels are rotatablymounted on the planet carrier, which is fixedly connected to the outputshaft, and an axially displaceable ring gear wheel, which surrounds andengages the planet gear wheels.

In a known range gearbox, the low range gear position and the high rangegear position are obtained by displacing the ring gear wheel axiallybetween the low range gear position, in which the ring gear wheel isrotationally locked relative to the gearbox housing, and the high rangegear position in which the ring gear wheel is rotatable relative to thegearbox housing and where the ring gear wheel, the planet gear wheelsand the sun gear wheel rotate as a common unity. The known planetarygear comprises two coupling rings on each side of the ring gear wheeland two synchronizing rings arranged on each side of the ring gearwheel. Synchronizer rings provide a synchronous shift.

The document WO0155620 discloses a synchronization device in a planetarygear in a range gearbox. The planetary gear includes a sun gear wheel, aplanet carrier and a ring gear wheel. The sun gear wheel is rotatablyconnected with the input shaft and a number of planet gear wheelsengaging the sun gear wheel, which planet gear wheels are rotatablymounted on the planet carrier, which is connected to the output shaft.An axially displaceable ring gear wheel surrounds and meshes with theplanet gear wheels. Low and high gear are obtained by displacing thering gear wheel axially between low range gear and high range gear.

However, there are range gearboxes in which synchronization devices arereplaced with coupling sleeves provided with splines. By controlling thetransmission to synchronous speed between the two components to beengaged, an axial displacement of the coupling sleeve along the twocomponents is made possible in order to connect them. When thecomponents should be detached, the transmission is controlled so thattorque balance occurs between the components so that the coupling sleeveis not transmitting torque. It then becomes possible to move thecoupling sleeve along the components in order to disengage them fromeach other.

The document U.S. Pat. No. 6,196,944 shows a planetary gear comprising asun gear wheel, a planet carrier with planet gear wheels and a ring gearwheel. The sun gear wheel may be connected to the input shaft by meansof a coupling sleeve in a low range gear position and disengaged fromthe input shaft in a high range gear position. In the high range gearposition, the input shaft is connected to the planet carrier by means ofthe same coupling sleeve. The ring gear wheel is firmly connected to agearbox housing. The known planetary gear is arranged in an auxiliarygearbox, having only two gear positions.

The reverse gear in a transmission in a vehicle is often arranged in themain gearbox, which then comprises a gear that is engaged when thevehicle is to be driven in the reversed direction. The gear wheel, whichis intended for the reverse gear, causes an elongation of the maingearbox, and an undesired increase in weight of the vehicle.

The document WO2015/183153A1 shows a gearbox for vehicles comprising arange gearbox provided with first, second and third axially movablecoupling sleeves acting on a planetary gear in the range gearbox.Depending on the axial position of the coupling sleeves, a reverse gearin the gearbox may be achieved.

The range gearbox must have a diameter, a length and a weight withinreasonable limits. If the diameter of the planetary gear in the rangegearbox is too large, the gearbox will not fit in a vehicle due togeometrical and design limits of the vehicle. An increased diameter ofthe planetary gear in the range gearbox also results in an increasedweight, which results in an increased overall weight of the vehicle.This may lead to increased fuel consumption of the vehicle.

When the planetary gear in the range gearbox is designed with a limiteddiameter, the gear ratio in the range gearbox will be limited to acertain amount. This may affect the driveability of the vehicle in thereverse direction since the vehicle may not be driven with a velocitylow enough in the reverse direction when a clutch between an engine andthe gearbox is completely engaged.

Since the gearbox must transmit a considerable amount of torque, thegear ratio may not be increased by minimizing the diameter of the sungear wheel. If the sun gear wheel has a very small diameter, it may notwithstand the considerable amount of torque needed. Also, by using asmall sun gear wheel, the diameter of the planet gear wheels may getinto physical contact with each other due to an increased diameter ofthe planet gear wheels.

SUMMARY OF THE INVENTION

There is a need for a gearbox provided with a reverse gear in a rangegearbox. There is also a need for a gearbox where all components in thegearbox are utilized effectively, so that low energy is required whenshifting. There is also a need for a gearbox, which exhibits smalldimensions relative to the possible transmission of torque. Also, thereis a need to develop a gearbox which brings the overall components inthe gearbox to a minimum in order to save manufacturing and repaircosts.

The object of the present invention is therefore to further develop agearbox provided with a reverse gear in a range gearbox.

Another object of the present invention is to provide a gearbox whichbrings the overall components in the gearbox to a minimum in order tosave manufacturing and repair costs.

A further object of the invention to provide a gearbox that utilizes allof the transmission components effectively.

A further object of the invention is to provide a gearbox having smalldimensions in relation to possible transmission of torque.

A further object of the present invention is to provide a gearbox whichrequires low energy for shifting.

These objects are achieved with the above-mentioned gearbox accordingdisclosed herein.

According to an aspect of the invention, a gearbox for vehicles isprovided. The gearbox comprises a split gearbox, a main gearbox and arange gearbox, which is shiftable into a low range gear, a high rangegear and a reverse gear. The range gearbox comprising a planetary gearwith a ring gear wheel, a sun gear wheel and a planet carrier, on whichat least one planet gear is rotatably mounted. The ring gear wheel andthe sun gear wheel engage with the at least one planet gear. A gearboxhousing surrounds the planetary gear. A first axially movable couplingsleeve is arranged to engage the planet carrier with the gearboxhousing. A second axially movable coupling sleeve is arranged to engagethe ring gear wheel with an output shaft for shifting into the reversegear in the gearbox. The split gearbox and the main gearbox are togetherarranged to have a combined largest gear ratio, which is larger than thegear ratio in the planetary gear in the range gearbox when the planetarygear is shifted into the reverse gear.

The vehicle may be driven in the reverse direction when the planetarygear in the range gearbox is shifted into the reverse gear. When thegear ratio in the split gearbox and the main gearbox together have acombined largest gear ratio, which is larger than the gear ratio in theplanetary gear in the range gearbox, when the planetary gear is shiftedinto the reverse gear, the driveability of the vehicle in the reversedirection may be acceptable even though a clutch between an engine andthe gearbox is completely engaged. With such a combined or common gearratio in the split gearbox and the main gearbox in relation to the gearratio in the range gearbox, the vehicle may be driven in the reversedirection in a velocity which is low enough to have control over thevehicle. With such a combined gear ratio, the range gearbox may have alimited diameter and still the driveability of the vehicle in thereverse direction is not affected. A limited diameter of the rangegearbox will bring the overall components in the gearbox to a minimum,and thus manufacturing and repair costs will be saved. The sun gearwheel in the planetary gear may be provided with a diameter, whichwithstands the considerable amount of torque needed. Thus, there is noneed to increase the gear ratio of the planetary gear in the rangegearbox by minimizing the diameter of the sun gear wheel.

The gearbox is also designed so that the combined or common gear ratioin the split gearbox and the main gearbox have a ratio spread that islarge enough to drive the vehicle in the reverse direction at a velocitywhich is low enough to have control over the vehicle. The definition ofthe ratio spread is the largest common gear ratio of the split gearboxand the main gearbox divided by the minimum common gear ratio of thesplit gearbox and the main gearbox.

According to a further aspect of the invention, the split gearbox andthe main gearbox are together arranged to have a combined largest gearratio over 4:1, and the planetary gear in the range gearbox is arrangedto have a gear ratio less than 4:1 when shifted into the reverse gear.When the combined largest gear ratio in the split gearbox and the maingearbox together is over 4:1, the driveability of the vehicle in thereverse direction is acceptable even though the gear ratio less than 4:1in the planetary gear in the range gearbox. With such a common gearratio in the split gearbox and the main gearbox in relation to the gearratio in the range gearbox, the vehicle may be driven in the reversedirection at a velocity which is low enough to have control over thevehicle.

According to a further aspect of the invention, the gearbox is arrangedto have an overlapping gear ratio in at least the highest gear in thelow range gear position and at least the lowest gear in a high rangegear position. The overlapping gear ratio will increase the total gearratio in the gearbox. Such a gearbox brings the overall components inthe gearbox to a minimum and utilizes all of the transmission componentseffectively.

According to a further aspect of the invention, the gearbox is arrangedto have an overlapping gear ratio in the two highest gears in the lowrange gear position and the two lowest gears in a high range gearposition. The overlapping gear ratio in the two highest gears in the lowrange gear position and the two lowest gears in a high range gearposition will increase the total gear ratio in the gearbox. In this way,the vehicle may be driven in the reverse direction at a velocity whichis low enough to have control over the vehicle. The driveability of thevehicle in the reverse direction will be very good.

When the gearbox is arranged with a split gearbox, a main gearbox and arange gearbox when the planetary gear is shifted into the reverse gear,the gear wheels in the split gearbox and the main gearbox may be sodesigned that an overlapping gear ratio is achieved. The overlappinggear ratio in the two highest gears in the low range gear position andthe two lowest gears in a high range gear position will increase thetotal gear ratio spread in the gearbox. Such a gearbox brings theoverall components in the gearbox to a minimum and utilizes all of thetransmission components effectively.

According to a further aspect of the invention, the split gearboxcomprises an incoming gear and a split gear, and the gear ratio of thesplit gear is larger than the gear ratio of the incoming gear. When thegear ratio of the split gear is larger than the gear ratio of theincoming gear, the overall gear ratio of the gearbox may be increased.

According to a further aspect of the invention, the gear ratio of theincoming gear is in the range 0.9:1-1.1:1. When the gear ratio of theincoming gear is in the range 0.9:1-1.1:1, the overall gear ratio of thegearbox may be increased and the vehicle may be driven in the reversedirection at a velocity which is low enough to have control over thevehicle. Thus, the driveability of the vehicle in the reverse directionwill be acceptable. The overall dimensions of the gearbox can bereduced. In addition, there is no need to increase the gear ratio of theplanetary gear in the range gearbox by minimizing the diameter of thesun gear wheel.

According to a further aspect of the invention, the gear ratio of theincoming gear is in the range 0.95:1-1.05:1. When the gear ratio of theincoming gear is in the range 0.95:1-1.05:1, the overall gear ratio ofthe gearbox may be increased and the vehicle may be driven in thereverse direction at a velocity which is low enough to have control overthe vehicle. Thus, the driveability of the vehicle in the reversedirection will be improved. The overall dimensions of the gearbox can bereduced further. In addition, there is no need to increase the gearratio of the planetary gear in the range gearbox by minimizing thediameter of the sun gear wheel.

According to a further aspect of the invention the gear ratio of theincoming gear is 1:1. When the gear ratio of the incoming gear is 1:1,the overall gear ratio of the gearbox may be increased and the vehiclemay be driven in the reverse direction at a velocity which is low enoughto have control over the vehicle. Thus, the driveability of the vehiclein the reverse direction will be very good. The overall dimensions ofthe gearbox can be reduced even further. In addition, there is no needto increase the gear ratio of the planetary gear in the range gearbox byminimizing the diameter of the sun gear wheel.

According to a further aspect of the invention, the split gearbox andthe main gearbox are together arranged to have a combined ratio spreadlarger than 5 and the planetary gear is arranged to have a gear ratioless than 4:1 when shifted into the reverse gear. With such a combinedratio spread in the split gearbox and the main gearbox, together withsuch a gear ratio in the range gearbox, the vehicle may be driven in thereverse direction at a velocity which is low enough to have control overthe vehicle. Thus, the driveability of the vehicle in the reversedirection is acceptable. The overall dimensions of the gearbox can bereduced. In addition, there is no need to increase the gear ratio of theplanetary gear in the range gearbox by minimizing the diameter of thesun gear wheel.

According to a further aspect of the invention, the split gearbox andthe main gearbox are together arranged to have a combined ratio spreadin the range 5.5-6.3 and the planetary gear is arranged to have a gearratio in the range 3.1:1-3.9:1 when shifted into the reverse gear. Withsuch a combined ratio spread in the split gearbox and the main gearbox,together with such a gear ratio in the range gearbox, the vehicle may bedriven in the reverse direction at a velocity which is low enough tohave control over the vehicle. Thus, the driveability of the vehicle inthe reverse direction is acceptable. The overall dimensions of thegearbox can be reduced. In addition, there is no need to increase thegear ratio of the planetary gear in the range gearbox by minimizing thediameter of the sun gear wheel.

According to a further aspect of the invention, the split gearbox andthe main gearbox are together arranged to have a combined ratio spreadin the range 5.7-6.1 and the planetary gear is arranged to have a gearratio in the range 3.3:1-3.6:1 when shifted into the reverse gear. Withsuch a combined ratio spread in the split gearbox and the main gearbox,together with such a gear ratio in the range gearbox, the vehicle may bedriven in the reverse direction at a velocity which is low enough tohave control over the vehicle. Thus, the driveability of the vehicle inthe reverse direction will be improved. The overall dimensions of thegearbox can be reduced further. In addition, there is no need toincrease the gear ratio of the planetary gear in the range gearbox byminimizing the diameter of the sun gear wheel.

The above-mentioned objects are also achieved by a vehicle, includingthe above-mentioned gearbox, according to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description of, as examples, preferred embodiments of theinvention with reference to the enclosed drawings, in which:

FIG. 1 shows schematically a side view of a vehicle with a gearboxaccording to the invention,

FIG. 2 shows schematically a cross section of the main gearbox and asplit gearbox according to the invention,

FIG. 3 shows schematically a cross section of the gearbox according tothe invention in a low range gear position,

FIG. 4 shows schematically a cross section of the gearbox according tothe invention in a high range gear position, and

FIG. 5 shows schematically a cross section of the gearbox according tothe invention in a reverse position.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 shows schematically a side view of a vehicle 1, provided with apowertrain 3, which comprises a gearbox 2 according to the invention.The powertrain 3 also comprises an internal combustion engine 4, apropeller shaft 10 and drive wheels 8. The drive wheels 8 are coupled tothe gearbox 2 via the propeller shaft 10. The gearbox 2 comprises arange gearbox 15B which aims to double the number of gear opportunities.The gearbox 2 is surrounded by a gearbox housing 12.

FIG. 2 shows a schematic sectional view of a gearbox 2 according to thepresent invention. The gearbox 2 comprises a main gearbox 15A, a splitgearbox 15C and the range gearbox 15B. The range gearbox 15B isshiftable into a low range gear, a high range gear and a reverse gear,which will be explained in more detail below. The vehicle 1 may bedriven in the reverse direction when the range gearbox 15B is shiftedinto the reverse gear. The combined gear ratio in the split gearbox 15Cand the main gearbox 15A together may be larger than the gear ratio in aplanetary gear 14 (FIG. 3) in the range gearbox 15B, when the planetarygear 14 is shifted into the reverse gear. The split gearbox 15C and themain gearbox 15A may together be arranged to have a combined largestgear ratio over 4:1 and the planetary gear 14 in the range gearbox 15Bmay be arranged to have a gear ratio less than 4:1 when shifted into thereverse gear. With such a common or combined gear ratio in the splitgearbox 15C and the main gearbox 15A in relation to the gear ratio inthe range gearbox 15B, the vehicle 1 may be driven in the reversedirection at a velocity which is low enough to have control over thevehicle 1 even though a clutch 11 between the engine 4 and the gearbox 2is completely engaged. The velocity of the vehicle 1 driven in thereverse direction at a gear with the gear ratio mentioned above and withthe clutch 11 completely engaged will be below three km/h.

In order to arrange the above mentioned gear ratio in the gearbox 2, thetwo highest gears in the low range gear position and the two lowestgears in a high range gear position may be overlapping. Thus, the twohighest gears in the low range gear positions should have substantiallythe same gear ratio as the two lowest gears in a high range gearposition. However, at least the highest gear in the low range gearposition and at least the lowest gear in a high range gear positionshould be overlapping. Thus, at least the highest gear in the low rangegear positions should have substantially the same gear ratio as at leastthe lowest gear in a high range gear position. This overlapping gearratio will increase the ratio spread in the gearbox 2. This will bringthe overall number of components in the gearbox 2 to a minimum and alsoutilize all of the transmission components effectively. The definitionof the ratio spread is the largest common or combined gear ratio of thesplit gearbox 15C and the main gearbox 15A divided with the minimumcommon or combined gear ratio of the split gearbox 15C and the maingearbox 15A.

The split gearbox 15C comprises an incoming gear 17 and a split gear 19.The gear ratio of the split gear 19 may be larger than the gear ratio ofthe incoming gear 17, so that the overall gear ratio in the gearbox 2may be increased. As an example, the gear ratio of the incoming gear 17may be in the range 0.9:1-1.1:1 and thus the gear ratio of the splitgear 19 may be larger than 0.9:1-1.1:1. When the gear ratio of theincoming gear 17 is in the range 0.9:1-1.1:1, the overall gear ratio ofthe gearbox 2 may be increased and the vehicle 1 may be driven in thereverse direction in a low enough velocity for a driver of the vehicle 1to have control over the vehicle 1. Thus, the driveability of thevehicle 1 in the reverse direction will be acceptable. The overalldimensions of the gearbox 2 can be reduced. Also, there is no need toincrease the gear ratio of the planetary gear 14 in the range gearbox15B by minimizing the diameter of the sun gear wheel 18.

According to another example the gear ratio of the incoming gear 17 maybe in the range 0.95:1-1.05:1 and thus the gear ratio of the split gear19 may be larger than 0.95:1-1.05:1. When the gear ratio of the incominggear 17 is in the range 0.95:1-1.05:1, the overall gear ratio of thegearbox 2 may be increased and the vehicle 1 may be driven in thereverse direction in a low enough velocity for a driver of the vehicle 1to have control over the vehicle 1. Thus, the driveability of thevehicle 1 in the reverse direction will be improved. The overalldimensions of the gearbox 2 can be reduced further. Also, there is noneed to increase the gear ratio of the planetary gear 14 in the rangegearbox 15B by minimizing the diameter of the sun gear wheel 18.

The gear ratio of the incoming gear 17 may also be substantially 1:1 andthus the gear ratio of the split gear 19 may be larger than 1:1. Whenthe gear ratio of the incoming gear 17 is substantially 1:1, the overallgear ratio of the gearbox 2 may be increased and the vehicle 1 may bedriven in the reverse direction in a velocity which is low enough for adriver of the vehicle 1 to have control over the vehicle 1. Thus, thedriveability of the vehicle 1 in the reverse direction will be verygood. The overall dimensions of the gearbox 2 can be reduced evenfurther. Also, there is no need to increase the gear ratio of theplanetary gear 14 in the range gearbox 15B by minimizing the diameter ofthe sun gear wheel 18.

The split gearbox 15C and the main gearbox 15A may together be arrangedto have a combined ratio spread in the range 5.5-6.3 and the planetarygear 14 may be arranged to have a gear ratio in the range 3.1:1-3.9:1when shifted into the reverse gear. With such a combined ratio spread inthe split gearbox 15C and the main gears box 15A together with such agear ratio in the range gearbox 15B, the vehicle 1 may be driven in thereverse direction in a velocity which is low enough for a driver of thevehicle 1 to have control over the vehicle 1. Thus, the driveability ofthe vehicle 1 in the reverse direction will be acceptable. The overalldimensions of the gearbox 2 can be reduced. In addition, there is noneed to increase the gear ratio of the planetary gear 14 in the rangegearbox 15B by minimizing the diameter of the sun gear wheel 18.

Alternatively, the split gearbox 15C and the main gearbox 15A maytogether be arranged to have a combined ratio spread in the range5.7-6.1 and the planetary gear 14 is arranged to have a gear ratio inthe range 3.3:1-3.6:1 when shifted into the reverse gear. With such acombined ratio spread in the split gearbox 15C and the main gearbox 15Atogether with such a gear ratio in the range gearbox 15B, the vehicle 1may be driven in the reverse direction in a low enough velocity for adriver of the vehicle 1 to have control over the vehicle 1. Thus, thedriveability of the vehicle 1 in the reverse direction will be improved.The overall dimensions of the gearbox 2 can be reduced further. Also,there is no need to increase the gear ratio of the planetary gear 14 inthe range gearbox 15B by minimizing the diameter of the sun gear wheel18.

According to FIG. 2 the main gearbox 15A alone can be set to fourdifferent gear ratios. The range gearbox 15B is arranged downstream themain gearbox 15A. The range gearbox 15B is surrounded by a gearboxhousing 12 and is discussed further with reference to FIGS. 3-5. Thesplit gearbox 15C is located upstream of the main gearbox 15A in thedirection of torque from combustion engine 4 to drive wheels 8. Thesplit gearbox 15C provides for each gear of the main gearbox 15A intotwo gear steps with different gear ratios in order to provide more gearratios of the gearbox 2.

Instead of a disengageble clutch 11 an arrangement with first and secondelectrical machines (not disclosed) may be arranged to rotate and brakea planetary gear (not disclosed) arranged in the powertrain 3 andlocated upstream the gearbox 2. In such an arrangement the firstelectrical machine may be arranged at a sun gear wheel (not disclosed)of the planetary gear 14, and the second electrical machine should bearranged at the first ring gear wheel (not disclosed) of the planetarygear. The first and second electrical machines may be the power sourceor may form part of the power source.

With regard to the main gearbox 15A, a layshaft 202 comprises gearwheels 203A, 204A, 205A that are rotatably fixed to the layshaft 202.For example, gear wheel 203A represents the second gear, gear wheel 204Athe first gear and gear wheel 205A the third gear. A mainshaft 206comprises corresponding gear wheels 203B, 204B, 205B which rotate freelyin relation to the mainshaft 206, but which can be selectively lockedfor rotation with the mainshaft 206 in order to engage a gear. Forexample, the second main gearbox gear can be engaged by maneuvering afirst main sleeve 207, arranged to rotate with the mainshaft 206, to aposition where the gear wheel 203B is engaged, i.e. to the left in thefigure, thereby bringing the gear wheel 203B to rotate the mainshaft 206and thereby also engaging the layshaft 202 to the mainshaft 206 via gearwheel 203A. Each pair of gear wheels on the layshaft 202 and mainshaft206 representing a gear ratio.

The first main gearbox gear can be engaged by disengaging the first mainsleeve 207 from gear wheel 203B and instead moving a second main sleeve208 to a position to the right in the figure where, instead, gear wheel204B is engaged, thereby bringing the gear wheel 204B to rotate themainshaft 206. Correspondingly, the third main gearbox gear can beengaged by maneuvering the second main sleeve 208 to a position to theleft in the figure where, instead gear wheel 205B is engaged, therebysetting the main gearbox 15A to third gear. Each of the first throughthird gears is used for a plurality of the total number of gearsprovided by the gearbox 2 as a whole. For example, the first gear of themain gearbox 15A will be used for first and second gear of the gearbox2, low and high split, low range, and also for seventh and eighth gear,low and high split, and high range. The different gears in the splitgearbox 15C and the main gearbox 15A may also be used when the rangegearbox 15B is shifted into the reverse gear.

The main gearbox 15A is also provided with a crawler gear 211 comprisinga crawler gear wheel pair 211A and 211B. The crawler gear wheel 211A isarranged on the layshaft and the crawler gear wheel 211B may rotatefreely in relation to the mainshaft 206, but can be selectively lockedfor rotation with the mainshaft 206 in order to engage the crawler gear211.

Further, with regard to the split gearbox 15C, the incoming gear 17comprises an incoming gear wheel 209A that, similar to the above, isrotatably fixed to the layshaft 202 and a corresponding incoming gearwheel 209B rotating freely in relation to the input shaft 201 but whichcan be selectively locked for rotation with the input shaft 201 througha split sleeve 210, which may be provided with a split synchronisingunit. The split sleeve 210 can further be used to connect the gearboxinput shaft 201 to gear wheel 205B directly. The incoming gear 17comprising the gear wheel pair 209A-B can together with the split sleeve210 thereby provide two different split gear ratios for each gear of themain gearbox 15A.

When e.g. the first gear is engaged, the split sleeve 210 is arranged toengage split gear wheel 205B. This will have the result that the inputshaft 201 is directly connected to the split gear wheel 205B, which viathe split gear wheel 205A establishes a first gear ratio between inputshaft 201 and layshaft 202. Gear wheel 205B, however, is not connectedto the mainshaft 206, but the layshaft 202 is connected to mainshaft 206through gear wheel pair 204A-B and by means of the second main sleeve208.

When the second gear is engaged, i.e. high split of a first main gearboxgear, the vehicle 1 is instead driven with gear wheel pair 209A-Bengaged, resulting in a second gear ratio between an input shaft 201 andlayshaft 202. The gear wheel 204B is still engaged by the second mainsleeve 208 according to the above, thereby extending the range of eachgear.

This split can be performed for each gear of the main gearbox 15A.However, when the coupling unit 210 engages gear wheel 205B and also thesecond main sleeve 208 engages gear wheel 205B a gear ratio of 1:1through the split gearbox 15C and the main gearbox 15A is obtained.

The crawler gear 211 according to the invention is engaged when areverse gear is engaged in the range gearbox 15B. A first reverse gearis engaged when also the split sleeve 210 is arranged to engage splitgear wheel 205B. This will have the result that the input shaft 201 isdirectly connected to the split gear wheel 205B, which via the splitgear wheel 205A establishes a gear ratio between input shaft 201 andlayshaft 202.

The crawler gear 211 is also engaged when the gearbox 2 is shifted intothe forward direction when the range gearbox 15B is shifted into the lowrange position, but not in the high range position. In comparison toother gears used when driving a vehicle 1 in the forward direction, suchas the gear wheel pair 204A-B representing the first gear in the maingearbox 15A, the reverse gear is less used and also the crawler gear 211in the forward direction is less used. Also, the torque transferredthrough the crawler gear 211 is less than the torque transferred throughother gears in the gearbox 2, such as the gear wheel pair 204A-B, due tothe high gear ratio in the crawler gear 211. For this reason wear of thecrawler gear wheel pair 211A and 211B will be limited.

According to FIG. 2 the crawler gear 211 is arranged in the main gearbox15A. However, it may also be possible to arrange the crawler gear 211 inthe split gearbox 15C, so that the crawler gear wheel 211A is arrangedon the input shaft 201 and the crawler gear wheel 211B is arranged onthe layshaft 202.

FIG. 3 shows a schematic sectional view of a gearbox 2 of the presentinvention. The gearbox 2 comprises a main gearbox 15A, a split gearbox15C and the range gearbox 15B. The range gearbox 15B comprises aplanetary gear 14 which has a low and a high gear, so that the switchingcapability of the gearbox 2 can be divided into a low range gearposition and a high range gear position. In a first gear positioncorresponding to the low range gear position a downshift takes place inthe planetary gear 14. In the high range gear position the gear ratio is1:1 in the planetary gear 14. The planetary gear 14 is in FIG. 3 shiftedinto the first gear position, corresponding to the low range gearposition.

The range gearbox 15B is accommodated in the gearbox housing 12 andcomprises a range gearbox input shaft 16 which may be a mainshaft 26 ofthe main gearbox 15A. The planetary gear 14 comprises three maincomponents which are rotatable arranged in relation to each other,namely a sun gear wheel 18, a planet carrier 20 and a ring gear wheel22. A number of planet gear wheels 24 are rotatable arranged withbearings on the planet carrier 20. With knowledge of the number of teeth32 of sun gear wheel 18 and the ring gear wheel 22, the relative gearratio of the three components can be determined. The sun gear wheel 18is rotatable connected to the input shaft 16 and the planet gear wheels24 engage the sun gear wheel 18. The ring gear wheel 22 surrounds andengages the planet gear wheels 24.

A first axially displaceable coupling sleeve 42 is in a first gearposition arranged to connect the transmission case 12 with the ring gearwheel 22 and in a second gear position arranged to disconnect thetransmission case 12 from the ring gear wheel 22. The first axiallymovable coupling sleeve 42 is in the first gear position arranged todisconnect the input shaft 16 from the planet carrier 20.

A second axially displaceable coupling sleeve 43 is in a third gearposition arranged to couple the ring gear wheel 22 with an output shaft28 of the gearbox 2. The output shaft 28 is coupled to the propellershaft 10 of the vehicle 1. In the third gear position, corresponding toa reverse gear, the first axially displaceable coupling sleeve 42 isarranged to disconnect the input shaft 16 from the planet carrier 20 andinstead is arranged to interconnect the planet carrier 20 with thegearbox housing 12. In the first and second gear positions the secondaxially displaceable coupling sleeve 43 is arranged to interconnect theplanet carrier 20 with the output shaft 28.

The first axially displaceable coupling sleeve 42 is on an inner surfaceprovided with first splines 50 arranged to interact with thecorresponding first splines 50 arranged on the ring gear wheel 22 and onthe periphery of a projection 52 which is fixedly connected to thetransmission housing 12. The first splines 50 on the first axiallydisplaceable coupling sleeve 42 are also arranged to cooperate withcorresponding first splines 50 arranged on the input shaft 16.Corresponding first splines 50 disposed on the input shaft 16 are madeon the periphery of a first sprocket 46 which is mounted on a shaft 38for the sun gear wheel 18. The first splines 50 on the first axiallydisplaceable coupling sleeve 42 are also arranged to cooperate withcorresponding first splines 50 arranged on the planet carrier 20.Corresponding first splines 50 disposed on the planet carrier 20 aremade on the periphery of a second sprocket 44 which is mounted on theplanet carrier 20.

The second axially displaceable coupling sleeve 43 is on an innersurface provided with second splines 51 which are arranged to cooperatewith corresponding second splines 51 arranged on the ring gear wheel 22,the planet carrier 20 and the output shaft 28. The corresponding secondsplines 51 arranged on the planet carrier 20 are formed on the peripheryof a third sprocket 49 which is mounted on the planet carrier 20. Thecorresponding second splines 51 provided on the output shaft 28 areformed on the periphery of a fourth sprocket 53 which is mounted on theoutput shaft 28.

The low gear in the gearbox 2 is obtained by displacing the firstcoupling sleeve 42, so that the ring gear wheel 22 is connected to thegearbox housing 12. The axial displacement of the first and secondcoupling sleeves 42, 43 are provided with a first and second shift fork60, 61 arranged in an outside circumferential groove 62 in therespective coupling sleeve 42, 43. The first shift fork 60 is influencedby a first power means 66 and the second shift fork 61 is influenced bya second power means 67. The first and second power means 66, 67 may bea pneumatic or hydraulic cylinder. The shift forks 60, 61 and powermeans 66, 67 are schematically shown in FIG. 3.

Preferably, the coupling sleeves 42, 43 each has a low weight, whichmeans that there is a need of low energy and force to move therespective coupling sleeves 42, 43 when shifting gears. This allows aquick gear shifting between the different gear positions in the gearbox2.

FIG. 4 shows a schematic sectional view of the range gearbox 15B in thesecond gear position or high range gear position in which the firstcoupling sleeve 42 is shifted to the right in FIG. 4 for connecting theinput shaft 16 to the planet carrier 20. In this position the firstcoupling sleeve 42 has disconnected the ring gear wheel 22 of thegearbox housing 12. The transmission of torque from the input shaft 16to the output shaft 28 is in the high range gear position via the inputshaft 16 and planet carrier 20 and further to the output shaft 28 viathe second coupling sleeve 43, so that the gear ratio through theplanetary gear 14 becomes 1:1. As an alternative, the second axiallymovable coupling sleeve 43 may in the second gear position be arrangedto engage the ring gear wheel 22 with the output shaft 28.

In FIG. 5 the range gearbox 15B has been shifted into the third gearposition, which is the reverse gear. The second axially displaceablesleeve 43 is in the third gear position arranged to connect the ringgear wheel 22 with output shaft 28. Thus, the second coupling sleeve 43is shifted by the second shift fork 61, so that the ring gear wheel 22is connected to the output shaft 28. The first coupling sleeve 42 isshifted by the first shift fork 60 to couple the planet carrier 20 withthe gearbox housing 12. The planet carrier 20 is provided with a secondsprocket 44 arranged for connecting the planet carrier 20 with thegearbox housing 12 by means of the first coupling sleeve 42. Thedisplacement of the respective clutch sleeve 42, 43 is performed whenthe input and the output shaft 16, 28 are stationary, which correspondsto a stationary operating state of the vehicle 1, when the range gearbox15B is included in the transmission 3 of a vehicle 1. In order toprovide a stationary position of the input shaft 16 the clutch 11 of thevehicle 1 is transferred to a disconnected mode. When the range gearbox15B is operated in the third gear position, torque is transmitted fromthe input shaft 16 to the sun gear wheel 18 and further to the planetgear wheels 24 which transmits the torque to the ring gear wheel 22 andfurther to the output shaft 28 via the second coupling sleeve 43. Theplanet carrier 20 is stationary as the first coupling sleeve 42 connectsthe planet carrier 20 with the gearbox housing 12.

With the gear ratio mentioned above, the range gearbox 15B may have alimited diameter and still the driveability of the vehicle 1 in thereverse direction is not adversely affected. A limited diameter of therange gearbox 15B will bring the overall components in the gearbox 2 toa minimum, and thus manufacturing and repair costs will be saved. Thesun gear wheel 18 in the planetary gear 14 may be provided with adiameter which withstands the considerable amount of torque needed.Thus, there is no need to increase the gear ratio of the planetary gear14 in the range gearbox 15B by minimizing the diameter of the sun gearwheel 18.

An electronic control unit 70 is coupled to the powertrain 3 to achievethe gear shifting above. A number of not shown speed sensors in thepowertrain 3 may be connected to the control unit 70. Another computer72 may also be connected to the control unit 70. The control unit 70 maybe a computer with appropriate software for this purpose. The controlunit 70 and/or the computer 72 comprise a computer program P, which caninclude routines to control the gearbox 2 of the present invention. Theprogram P may be stored in an executable form or compressed form in amemory M and/or in a read/write memory. Preferably, there is provided acomputer program product comprising a program code stored on a, by acomputer readable medium for performing the gear shifting above, whenthe program is run on the control unit 70 or another computer 72connected to the control unit 70. The code may be non-volatile, storedin the computer readable medium.

The components and features specified above may within the framework ofthe invention be combined between the different embodiments specified.

The invention claimed is:
 1. A gearbox for vehicles, comprising: a splitgearbox, a main gearbox and a range gearbox, and the gearbox isshiftable into a low range gear, a high range gear and a reverse gear;the range gearbox comprising a planetary gear with a ring gear wheel, asun gear wheel and a planet carrier, on which at least one planet gearwheel is rotatably mounted; the ring gear wheel of the range gearbox andthe sun gear wheel of the range gearbox engage with the at least oneplanet gear wheel; a gearbox housing surrounding the planetary gear; afirst axially movable coupling sleeve arranged to engage the planetcarrier with the gearbox housing; and a second axially movable couplingsleeve arranged to engage the ring gear wheel with an output shaft forachieving the reverse gear in the gearbox, the split gearbox and themain gearbox are together arranged to have a combined largest gearratio, which is larger than a gear ratio in the planetary gear in therange gearbox when the planetary gear is shifted into the reverse gear.2. The gearbox according to claim 1, wherein the split gearbox and themain gearbox are together arranged to have a combined largest gear ratioover 4:1 and the planetary gear in the range gearbox is arranged to havea gear ratio less than 4:1 when shifted into the reverse gear.
 3. Thegearbox according to claim 1, further comprising the gearbox is arrangedto have an overlapping gear ratio in at least a highest gear in a lowrange gear position and at least a lowest gear in a high range gearposition.
 4. The gearbox according to claim 3, wherein the gearbox isarranged to have an overlapping gear ratio in two of the highest gearsin the low range gear position and two of the lowest gears in a highrange gear position.
 5. The gearbox according to claim 1, furthercomprising the split gearbox comprises an incoming gear and a splitgear; and a gear ratio of the split gear is larger than a gear ratio ofthe incoming gear.
 6. The gearbox according to claim 5, wherein the gearratio of the incoming gear is in the range 0.9:1-1.1:1.
 7. The gearboxaccording to claim 5, wherein the gear ratio of the incoming gear is inthe range 0.95:1-1.05:1.
 8. The gearbox according to claim 5, whereinthe gear ratio of the incoming gear is 1:1.
 9. The gearbox according toclaim 1, further comprising the split gearbox and the main gearbox aretogether arranged to have a combined ratio spread larger than 5 and theplanetary gear is arranged to have a gear ratio less than 4:1 whenshifted into the reverse gear.
 10. The gearbox according to claim 1,further comprising the split gearbox and the main gearbox are togetherarranged to have a combined ratio spread in the range 5.5-6.3 and theplanetary gear is arranged to have a gear ratio in the range 3.1:1-3.9:1when shifted into the reverse gear.
 11. The gearbox according to claim1, further comprising the split gearbox and the main gearbox aretogether arranged to have a combined ratio spread in the range 5.7-6.1and the planetary gear is arranged to have a gear ratio in the range3.3:1-3.6:1 when shifted into the reverse gear.
 12. A vehicle,comprising a gearbox according to claim 1.